From owner-freebsd-arch@FreeBSD.ORG Wed Feb 25 00:23:04 2015 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 4529CE1; Wed, 25 Feb 2015 00:23:04 +0000 (UTC) Received: from gold.funkthat.com (gate2.funkthat.com [208.87.223.18]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "gold.funkthat.com", Issuer "gold.funkthat.com" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id EFAAC180; Wed, 25 Feb 2015 00:23:03 +0000 (UTC) Received: from gold.funkthat.com (localhost [127.0.0.1]) by gold.funkthat.com (8.14.5/8.14.5) with ESMTP id t1P0N1jp007020 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Tue, 24 Feb 2015 16:23:01 -0800 (PST) (envelope-from jmg@gold.funkthat.com) Received: (from jmg@localhost) by gold.funkthat.com (8.14.5/8.14.5/Submit) id t1P0N1wI007019; Tue, 24 Feb 2015 16:23:01 -0800 (PST) (envelope-from jmg) Date: Tue, 24 Feb 2015 16:23:01 -0800 From: John-Mark Gurney To: "K. Macy" Subject: Re: locks and kernel randomness... Message-ID: <20150225002301.GS46794@funkthat.com> References: <20150224015721.GT74514@kib.kiev.ua> <54EBDC1C.3060007@astrodoggroup.com> <20150224024250.GV74514@kib.kiev.ua> <20150224174053.GG46794@funkthat.com> <54ECBD4B.6000007@freebsd.org> <20150224182507.GI46794@funkthat.com> <54ECEA43.2080008@freebsd.org> <20150224231921.GQ46794@funkthat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Operating-System: FreeBSD 9.1-PRERELEASE amd64 X-PGP-Fingerprint: 54BA 873B 6515 3F10 9E88 9322 9CB1 8F74 6D3F A396 X-Files: The truth is out there X-URL: http://resnet.uoregon.edu/~gurney_j/ X-Resume: http://resnet.uoregon.edu/~gurney_j/resume.html X-TipJar: bitcoin:13Qmb6AeTgQecazTWph4XasEsP7nGRbAPE X-to-the-FBI-CIA-and-NSA: HI! HOW YA DOIN? can i haz chizburger? User-Agent: Mutt/1.5.21 (2010-09-15) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.7 (gold.funkthat.com [127.0.0.1]); Tue, 24 Feb 2015 16:23:01 -0800 (PST) Cc: Konstantin Belousov , Harrison Grundy , Alfred Perlstein , "freebsd-arch@freebsd.org" X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 25 Feb 2015 00:23:04 -0000 K. Macy wrote this message on Tue, Feb 24, 2015 at 15:33 -0800: > > If someone does find a performance issue w/ my patch, I WILL work with > > them on a solution, but I will not work w/ people who make unfounded > > claims about the impact of this work... > > > > ... The concerns may be exaggerated, but they aren't > unfounded. Not quite the same thing, but no one wants to spend the Till someone shows me code in the kernel tree where this is even close to a performance problem, it is unfounded... I've asked, and no one has > cycles doing a SHA256 because it's "The Right Thing"(tm) when their > use case only requires a fletcher2. Depends upon what you're doing.. I haven't proposed changing ZFS's default to sha256, so stop w/ the false equivalences... > If it doesn't already exist, it might also be worth looking in to a > more scalable CSPRNG implementation not requiring locking in the > common case. For example, each core is seeded separately periodically > so that has a private pool that is protected by a critical section. > The private pool would be regularly refreshed by cpu-local callout. > Thus, a lock would only be acquired if the local entropy were > depleted. I'm not discussing this until you read and reply to my original email, since it's clear that my original email's contents has been ignored in this thread... -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."